The present invention relates to a composition, which contains a lung surfactant, for curing respiratory diseases.
As drugs for curing respiratory diseases, there are such antagonizers as antibiotics and chemotherapeutics besides antitussives, expectorants, bronchodilators, antiallergic drugs, antiinflammatory drug, anticancer drugs, etc. These medicines for curing respiratory diseases are used by general administration such as oral administration, intraveneous injection, intramuscular injection, etc.; however, in the case of some therapeutic medicines, especially antagonizers and antiallergic drugs like antasthmatics, the administration by means of inhalation or infusion is also adopted.
The administration of a drug by inhalation or infusion is what is called a local treatment effected by a direct application of a drug to the affected part and can be expected to produce less side effects as compared with the general administration of a drug mentioned above. However, the application of a drug by inhalation or infusion to the respiratory apparatus inclusive of naris, throat, trachea, lung, etc. sometimes results in the insufficient absorption of the drug through the mucous membrane depending upon the drug, thus it is at a disadvantage in being unable to achieve enough indirect remedial effect attributable to the increase of the concentration of the drug in the blood. Some drugs make it impracticable to administer the drug by inhalation or infusion as they irritate the mucous membrane of the respiratory tracts of the bronchi, etc. causing the emission of coughs.
On the other hand, the lung surfactant protects the respiratory epitheria by covering the inner walls of the alveoli of lung and also has a physiological function which is important for the animals to maintain their respiratory function properly. More particularly, the lung surfactant has a singular surface activity which makes the surface tension of the inner surface of the alveolium vary in accordance with the expiration and inspiration and contributes to the maintenance of interalveolium functional stabilization to exercise an anti-atelectatic action. It is known that this surfactant contains phospholipids, neutral lipids, protein, etc. as ingredients and has dipalmitoyl lecithin as a main ingredient. T. Fujiwara et al. recently reported that they obtained an artifically prepared lung surfactant having a higher surface activity by adding dipalmitoyl lecithin, etc. to a surfactant recovered from the bovine lung and that they achieved a good result for the therapy of indiopathic respiratory distress syndrome (IRDS) by the instillation of the said lung surfactant dispersion to the respiratory tracts of the premature babies (Pediatric Clinics, Vol. 32, No. 7, p.1335, 1979).